Tannin-rich tree bark extracts inhibit the development of bacteria associated with bovine mastitis

Abstract

Condensed tannins were quantified in the barks of selected tree species, and the antibacterial activity of these substances against clinical and subclinical isolates of bovine mastitis were evaluated. Tree barks from Mimosa tenuiflora, Mimosa caesalpiniifolia, Anacardium occidentale, and Stryphnodendron adstringens were used, as well as commercial tannin from Acacia mearnsii. The tannins were extracted using a mixture of ethyl alcohol and acetone. The moisture content (MC), Stiasny index (SI), total solids content (TSC), and condensed tannins (CT) were measured. The evaluation of antimicrobial activity was determined by applying the disk diffusion test. The species that showed the highest CT were M. tenuiflora and A. occidentale, with 37.3% and 37.3%, respectively. The highest SI were obtained by the species A. occidentale and M. caesalpiniifolia, with values above 90%. The bacterium with the lowest resistance to the use of tannins was Streptococcus uberis. A. mearnsii was the only one capable of inhibiting the growth of Escherichia coli, with a mean inhibition halo of 9 mm. All species under study showed high values of condensed tannins in their barks. In addition to showing good performance as antimicrobial agents, these tannins indicated potential applications in the development of natural medicines for the treatment of bovine mastitis.